JP2-120198 A discloses a suspension system for use in a vehicle, wherein a motor for driving the wheel is provided inside the wheel. In this suspension system, an outer portion of the motor, which corresponds to the rotor portion of the motor, is connected to a wheel disk, while an inner portion of the motor, which corresponds to the stator portion of the motor, is supported so as not to rotate with respect to a vehicle body.
In the conventional suspension system as disclosed in JP2-120198 A, there is no other choice but to dispose a braking system or a suspension arm on the central side of the vehicle with respect to the motor, because the motor occupies a large amount of space inside the wheel and substantially no available space remains around the center of the wheel due to existence of other components such as a hub. Concerning the steering wheel, in particular, a strong constraint is placed on an installing position and the shape of a suspension arm to avoid the interference between the suspension arm and the motor during steering operations. Thus, with such arrangements, functions required intrinsically for a suspension system cannot be achieved.
Further, with the arrangement in which the braking system is installed on the central side of the vehicle with respect to the motor, stronger constraint may be placed on the installing position of a suspension arm due to a disk rotor or a drum of the brake disk. Furthermore, this arrangement lowers a cooling characteristic of the braking system.